Tokyo-based Creative Man Productions is expanding its music festival Summer Sonic from two days to three this year.

Summer Sonic has been held simultaneously in Tokyo and Osaka on the first weekend in August for the past nine years. It will retain that calendar slot and add Friday to the bill. In the past, the billing for each day alternated between the two cities and the rotation of the line-ups is yet to be determined.

The Summer Sonic festival has risen from the relatively small venue of Fujikyu Highland in its first year, when it was held only in the Tokyo area, to seeing more than 50,000 now attend in each location.

Creative Man Productions president Naoki Shimizu told that increased international interest in the festival has led to the addition of the Friday.

"As Summer Sonic has shown tremendous growth over the decade, we consistently receive a huge amount of interest in Summer Sonic from artists across the world," he said.

He also alluded to the 10th anniversary as an impetus to add another day. "It is an honor for us to invite as many artists as possible for this special occasion, artists we believe we have grown with together, artists who are legendary, and new artists who we are eager to support," he said.

The 2009 line-up is still to be confirmed. Last year Summer Sonic was headlined by Coldplay and The Verve while 2007 saw the Black Eyed Peas, Artic Monkeys and Avril Lavigne top the bill.